Lazy loading of regions

Also adds landing page feature. But candidate list is hardcoded
for now. Example html file updated.

show method of lcd renamed to render.

Introduced a trigger searchclear
Introduced mw.uls.changeLanguage, setPreviousLanguages
getPreviousLanguages and getBrowserLanguage methods

Region groups re-numbered - from [4, 1, 2, 3] to [1, 2, 3, 4].

Change-Id: Iac1edf628708e6f40e41578df70d40c42f15289a

src/jquery.uls.languagefilter.js

@@ -78,8 +78,12 @@
 					var that = this;
 					this.selectedLanguage = null;
 					delay( function() {
-						that.options.$target.empty();
-						that.search();
+						if ( !that.$element.val() ) {
+							that.clear();
+						} else {
+							that.options.$target.empty();
+							that.search();
+						}
 					}, 300 );
 					this.toggleClear();
 			}
@@ -101,7 +105,7 @@
 		 */
 		clear: function() {
 			this.deactivate();
-			this.search();
+			this.$element.trigger( 'seachclear' );
 		},
 
 		/**